#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>
int main()
{
    char a[90] = { 0 }, b[90] = { 0 };
    gets(a);
    int i = 0, j = 0, t = 0, k = 0;
    for (i = 0; i < strlen(a); i++)
    {
        if (j == 0)
        {
            b[j] = a[i];
            j++;
        }
        else if (j > 0)
        {
            for (k = 0; k < j; k++)
            {
                b[k] = a[i];
                break;
            }
            if (k == j)
            {
                b[j] = a[i];
                j++;
            }
        }
    }
    int p = 0;
    do {
        p = 0;
        for (j = 0; j < strlen(a) - 1; j++)
        {
            if (b[j] > b[j + 1])
            {
                t = b[j];
                b[j] = b[j + 1];
                b[j + 1] = t;
                p++;
            }
        }
    } while (p != 0);
    for (j = 0; j < strlen(a); j++)
    {
        printf("%c", b[j]);
    }
    return 0;
}